1. Technical Field
The invention relates generally to a method for forming a high aspect ratio trench in a silicon substrate by contacting exposed silicon, under reactive ion etching (RIE) conditions, with an etchant which comprises oxygen, silicon and a halogen component. The etchant is also substantially free of hydrogen and carbon.
2. Related Art
Processes for the etching of silicon substrates, and particularly for the etching of deep trenches in silicon substrates, are known to be susceptible to certain deficiencies, such as varying silicon loads at the bottom of a trench due to diffusive gradients, and losses to trench sidewalls. Other relevant deficiencies include uniformity issues caused by mask erosion at the trench edges, and trench profile distortion, which may lead to the formation of side pockets in the trench walls in some severe cases.
Accordingly, there exists a need for an alternative deep trench etching method which makes the process less sensitive to silicon loading, achieves greater trench depth, and maintains or controls the trench profile.